Everyone would have a rating, so when people complain it would mean more than just that wasted L$ in sending it to where ever it goes. You could get a percentage based off any complaints (sent via right-click->more->comment->creator feedback) /divided by/ the number of objects sold. So average vendor Joe has sold 400 widgets, but 30 of his customers complained and gave "negative" feedback while only 12 gave "positive" and then the rest of them (35
who never voted automatically say "Neutral". Give a small space to enter a short comment why and...7.5% of his buyers said he sucked.
3% of his buyers actually liked it.
89.5% of his buyers didn't say anything.
Now looking at this in the game world I could make a more informed decision. The reason I even brought this up in the first place is because I was shopping with someone in a mall and they said they could not decide between three diff. products, so he went with one...it sucked and lacked features, and was forced to swallow that mistake and purchase the more expensive (but worth it) item.
This is no big deal on small stuff like shirts and hair, etc. but when you are buying things like prefab houses, scripts, etc. You would want to make a more informed decision before plopping down 4000 L's just like that!
EDIT: This would require a new menu item(s) in the pie menu for just the feedback. Also, it should cost like 10L to make a product review so when people put stuff in there they mean it! And you should be able to sort the user reviews by all negative, all positive, and also make sure that they are in order with more recent complaint on the top.